android-kotlin-api-design-reviewer

Kotlin API Design Review

Naming Rules

• Clear at point of use
• Omit needless words
• lowerCamelCase: properties, functions, variables
• UpperCamelCase: classes, interfaces, objects
• UPPER_SNAKE_CASE: constants
• Booleans: is, has, can, should prefix
• Collections: plural names (users, not userList)

Compose-specific Naming

• Composable functions returning Unit: use PascalCase nouns (e.g., UserProfileCard, not userProfile)
• Avoid spaces and backticked identifiers in function names, especially in public APIs (discouraged by Kotlin conventions)

Common Issues

Issue	Fix
var visible	var isVisible
fun getData()	fun getUserName()
var nameString	var name
userList	users
Composable named like regular function	Rename to PascalCase noun (ProfileScreen)
Implicit return type in library	Add explicit : String

Function Design

• Named parameters for clarity beyond first param
• Default parameters at end
• Suspend functions for async operations
• Extension functions for utility methods
• Operator overloading when semantically appropriate
• Prefer properties over parameterless functions when the operation is cheap and non-throwing
• Use named arguments + trailing commas for multi-parameter calls in public APIs

Return Types

• Nullable when null is meaningful
• Result for failable operations
• Flow for streams
• sealed class for finite states
• Explicitly declare return types in public library APIs (even if inferable)

Data Classes

• Use for data transfer objects
• Immutable by default (val over var)
• Copy function for updates
• Destructuring support

Public API / Library

• Provide KDoc for all public members
• Use @JvmName for interop-friendly naming
• Use backing properties (_internalValue) for observed state
• Consider type aliases for repeated complex function types